fix(doctests): Use lowercase server fixture instead of creating Server

Critical fix: The command_runner property doctest was creating
`Server(socket_name="default")` which would:

1. Get wrapped by TestServer factory (via conftest.py:44)
2. Get tracked with socket name "default" in created_sockets
3. Get killed by TestServer finalizer at test suite end
4. KILL THE USER'S ACTUAL TMUX SESSION if they ran tests from inside tmux

Solution: Use the lowercase `server` fixture that's already injected
into the doctest namespace (conftest.py:43). The fixture has a unique
socket name like `libtmux_test3k9m7x2q` that's properly tracked and
cleaned up without touching the user's session.

Also fixed 6 test violations that used hardcoded socket names or
reused fixture sockets:
- tests/test_command_runner.py: 4 tests now use TestServer fixture
- tests/control_mode/test_runner.py: 1 test uses TestServer
- tests/control_mode/test_benchmarks.py: 1 test uses TestServer

All tests now follow the proven pattern of using fixtures for unique
socket names and automatic cleanup.

Fixes: User's tmux session being killed when running `uv run pytest`

Author: tony

src/libtmux/server.py

@@ -204,7 +204,6 @@ def command_runner(self) -> CommandRunner:
 
         Examples
         --------
-        >>> server = Server(socket_name="default")
         >>> assert server.command_runner is not None
         >>> type(server.command_runner).__name__
         'SubprocessCommandRunner'

tests/control_mode/test_benchmarks.py

@@ -159,18 +159,22 @@ def test_benchmark_server_integration_subprocess(server: Server) -> None:
 
 
 @pytest.mark.benchmark
-def test_benchmark_server_integration_control_mode(server: Server) -> None:
+def test_benchmark_server_integration_control_mode(
+    TestServer: t.Callable[..., Server],
+) -> None:
     """Benchmark Server with control mode runner.
 
     This tests the performance of high-level Server API using control mode.
     Note: Operations with format strings still use subprocess fallback.
     """
-    assert server.socket_name
-    control_runner = ControlModeCommandRunner(server.socket_name)
+    # Create independent server with unique socket
+    test_server = TestServer()
+    assert test_server.socket_name
+    control_runner = ControlModeCommandRunner(test_server.socket_name)
 
     # Create server with control mode runner
     cm_server = Server(
-        socket_name=server.socket_name,
+        socket_name=test_server.socket_name,
         command_runner=control_runner,
     )
 

tests/control_mode/test_runner.py

@@ -223,18 +223,20 @@ def test_runner_preserves_output_format(server: Server, session: Session) -> Non
     control_runner.close()
 
 
-def test_runner_with_server_integration(server: Server) -> None:
+def test_runner_with_server_integration(TestServer: t.Callable[..., Server]) -> None:
     """Server works correctly with control mode runner.
 
     Control mode runner transparently falls back to subprocess for commands
     with format strings (-F flag), ensuring all operations work correctly.
     """
-    assert server.socket_name
-    runner = ControlModeCommandRunner(server.socket_name)
+    # Create independent server with unique socket
+    test_server = TestServer()
+    assert test_server.socket_name
+    runner = ControlModeCommandRunner(test_server.socket_name)
 
     # Create server with control mode runner
     cm_server = Server(
-        socket_name=server.socket_name,
+        socket_name=test_server.socket_name,
         command_runner=runner,
     )
 

tests/test_command_runner.py

@@ -30,16 +30,17 @@ def test_server_default_runner(server: Server) -> None:
     assert isinstance(server.command_runner, SubprocessCommandRunner)
 
 
-def test_server_custom_runner() -> None:
+def test_server_custom_runner(TestServer: t.Callable[..., Server]) -> None:
     """Server accepts custom command runner."""
     custom_runner = SubprocessCommandRunner()
-    server = Server(socket_name="test", command_runner=custom_runner)
+    server = TestServer()
+    server.command_runner = custom_runner
     assert server.command_runner is custom_runner
 
 
-def test_server_runner_lazy_init() -> None:
+def test_server_runner_lazy_init(TestServer: t.Callable[..., Server]) -> None:
     """Server lazily initializes command runner."""
-    server = Server(socket_name="test")
+    server = TestServer()
     # Access property to trigger lazy init
     runner = server.command_runner
     assert isinstance(runner, SubprocessCommandRunner)
@@ -113,10 +114,12 @@ def test_runner_with_test_server_factory(TestServer: t.Callable[..., Server]) ->
     assert isinstance(server2.command_runner, SubprocessCommandRunner)
 
 
-def test_backward_compatibility_no_runner_param(server: Server) -> None:
+def test_backward_compatibility_no_runner_param(
+    TestServer: t.Callable[..., Server],
+) -> None:
     """Server works without command_runner parameter (backward compatibility)."""
     # Create server without command_runner parameter
-    new_server = Server(socket_name=f"test_{server.socket_name}")
+    new_server = TestServer()
 
     # Should auto-initialize with SubprocessCommandRunner
     assert new_server.command_runner is not None
@@ -127,9 +130,9 @@ def test_backward_compatibility_no_runner_param(server: Server) -> None:
     assert hasattr(result, "stdout")
 
 
-def test_runner_setter() -> None:
+def test_runner_setter(TestServer: t.Callable[..., Server]) -> None:
     """Server.command_runner can be set after initialization."""
-    server = Server(socket_name="test")
+    server = TestServer()
 
     # Initial runner
     initial_runner = server.command_runner